Writing instrument



FIG. 1 is a bottom view of an ornamental design for a writing instrument design according to the present invention;

FIG. 2 is a top view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a perspective view thereof;

FIG. 6 is a rear view thereof; and,

FIG. 7 is a left view thereof. 

CLAIM The ornamental design for a writing instrument, as shown and described. 